WASHINGTON -- Iran, citing "fresh evidence," is expanding its investigation of two U.S. scholars imprisoned on unspecified charges.

"We have received fresh evidence," Iranian judiciary spokesman Alireza Jamshidi said Tuesday in a Washington Post report. "Fresh investigations have started based on this evidence."

Haleh Esfandiari, a director of the Middle East program at the Smithsonian's Woodrow Wilson International Center for Scholars, and Kian Tajbakhsh, a New York social scientist, are charged with unspecified crimes against Iran.

At least two other U.S. residents have been detained in Iran: California businessman Ali Shakeri and correspondent Parnaz Azima of U.S.-funded Radio Farda, The Washington Post reported Wednesday.

In addition, three Iranians who had been in the United States on a cultural exchange for filmmakers had their passports revoked when they returned to Iran Saturday and were told they must appear in court, the Post reported.